Who would want to retire into a bear market? Certainly stocks are roaring now, but the problem is, we never know when one will happen. Bear markets are defined as a decline in the S&P 500 Index of at least 20 percent from the previous high. They are not infrequent and have happened, on average, about every three years over the last 80 years, with an average decline of 35 percent. If you are unable to follow the link, please click here for a PDF Version.